Dont' load extension in custom.js

[Carreau]

Jupyter.utils.load_extensions("raw-button/raw-button"); is not the right way to do that.

use jupyter nbextension enable or alike, worse case write a script that modify

.jupyter/nbconfig/notebook.json to load the right extension. Pointing user to custom.js for extension is really last resort.

[captainsafia]

Thanks, I will fix across all the extensions.